With a refractometer, a refractive index of a substance can be measured. The refractive index of a substance or a sample depends from both the wavelength of the light and from its temperature. In order to make measuring results comparable, in refractometers, it is therefore often measured at specified wavelengths and temperatures. Deviations from standardized wavelengths or temperatures during measuring lead to measuring errors in many cases. In addition, there are measuring errors of the sensor technology which are specific for the respectively related measuring principle.
In refractometers and in other, in particular optical, measuring apparatuses inaccuracies may occur, if a temperature sensor for measuring the temperature of a sample carrier which is carrying the sample changes its properties over time.
Prior art is disclosed in EP 0,583,007, U.S. Pat. No. 7,064,816, U.S. Pat. No. 6,596,973, U.S. Pat. No. 8,280,674, U.S. Pat. No. 8,177,421, GB 2,266,271 and EP 2,100,112.